Carpenter, 2006. Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. In Foster,
J.R. and Lucas, S. G., eds., Paleontology and Geology of the Upper
Jurassic Morrison Formation. New Mexico Museum of Natural History and
Science Bulletin 36.

Cope, E.D., 1878. A new species of Amphicoelias: American Naturalist, v.12, p. 563-565.

Osborn, H.F. and Mook, C. C., 1921. Camarasaurus, Amphicoelias and other sauropods of Cope: Memoirs of the American Museum of Natural History NS, v. 3 (3), p. 249-387.

Mike, I can give a short version:A. fragillimus is often assumed to be a diplodocid, but based on what we know of it, entering in Whitlock (2011) analysis it turns out as a non-flagellicaudatan diplodocoid.Given that among the alternative placements of A.fragillimus there is as a basal rebbachisaurid, and given that A.fragillimus shares extensive lamination of the neural arch with rebbachisaurids, I speculated (as a mere hypothesis) that rebbachisaurids are dwarf descendant of a giant highly laminated sauropod like A. fragillimus. Extensive lamination of rebbachisaurids, under that hypothesis, would be a feature inherited from their giant ancestors.

In his paper Carpenter says he simply scaled up Diplodocus c.’s vertebra to 2.7 meters. The only problem is that he used the dimensions from Seismosaurus for diplodocus’s vert, but said the length of Diplodocus was only 26.25 meters. This small mistake of recording diplodocus’s vert as 1.22 meters instead of .946 meters has lead to the widespread belief that Amphicoelias was 60 meters long and 120 tons in weight. In reality using carpenter’s method with the correct numbers we get, 2.7/.946=2.864. 2.854×26.25 meters=75 meters long. Also 2.856^3=23.2. 23.2×12 tons=278 tons.

A quote from Zach Armstrong on the subject. (note, he uses a 11.5 ton Diplodocus)

I’m not sure where Carpenter got his mass and length estimates–since he says he basically says he just scaled it up isometrically. A 2.7 meter tall vertebra is 2.79 (270 cm/96.6 cm=2.79)times as tall as the D10 in D. carnegii which means a length of 69.75 meters if D. carnegii was 25 meters long or 73.23 meters if it was 26.25 meters like Carpenter assumes. A resulting mass estimate should then be 247.38 tonnes (2.79^3=21.7; 21.7*11.4 tonnes=247.38 tonnes)!

And this is assuming it was the 10th dorsal! What if it was the 9th? Scaling the vertebrae, we get 270/94.6=2.85; 2.85^3=23.14; 23.14*11.4tonnes=263.79 tonnes!

Adding intravetebral cartilage, which accounts for ~10% of the body lengths of most birds and reptiles, increases the dimensions even more.

These estimates are backed by scientific methods, and are the best way we have of guessing Amphicoelias’s dimensions.

Spread the word!

Measurement for Diplodocus’s vert is from: Osborn, H.F., and Mook, C. C. (1921). “Camarasaurus, Amphicoelias and other sauropods of Cope.”

"These estimates are backed by scientific methods, and are the best way we have of guessing Amphicoelias’s dimensions."False. The best way would be using a regression curve derived from a large sample of measurements, and not just a linear proportion.Thus, the exact size of A. fragillimus (assuming its vertebra was truly that big) remains unknown.

Dude it’s actually a simple mistake, just read the paper. And the guys at SV-POW have talked about the problem in the comments for the post about Amphicoelias. Paleontologists are not immune from mistakes, and guys behind laptops are not incapable of correcting them.

The sizes are not fully improbable! They are the most accurate estimate we have, are you paying attention? Every professional that has worked on Amphicoelias has agreed it’s basically a scaled up diplodocus, so Amphicoelias was most likely ~2.85 times as long as a 26.25 meter diplodocus.

In absence of a real specimen, all about A. fragillimus is merely a series of speculative opinions: nobody can falsify Cope's publication, so A. fragillimus is currently beyond science.Pending new bones, I don't care much about discussing again about it.

Sadly, I am not able to chat with a professional Paleontologist. But the fact is, I don't need to, the problem is as simple as a typo, just fix it and move on. Please read the paper yourself, and come to your conclusion

My conclusion is what I wrote above: a single page written in the XIX century does not represent a robust evidence for the existence a super-giant sauropod. As a paleontologist, I need more robust evidence. I'm not saying "it never existed", just: I need more evidence, and in absence of more evidence, I'm not interested in discussing more on this (boring) topic.

Sadly, I am not able to chat with a professional Paleontologist. But the fact is, I don't need to, the problem is as simple as a typo, just fix it and move on. Please read the paper yourself, and come to your conclusion. Here's my new scale, with an 85 meter Amphicoelias.

First, we must fill in missing info and estimate the length of Amphicoelias altus.

If we were to scale up using Diplodocus, we would get:~28.5 meters based on femur length, and,~25.4 meters based on LTV height.

If we were to scale up based on Barosaurus, we would get:33.04 meters based on femur length, and,~27.36 meters based on LTV height.

Amphicoelias fragillimus vertebra has been estimate to be 2.7 meters tall. Also, Greg Paul estimated it to be 2.4-2.6 meters tall.

To be as unbiased as possible, all three measurements will be used. That vertebra has been thought to be the last to second to last trunk vertebra.

We will assume it to be the last trunk vertebra for now.

Since the last trunk vertebra height of A. altus is 1.075 meters, A. fragillimus would have dimensions ~2.512 times that of A. altus based on a 2.7-meter LTV height, ~2.42 times based on 2.6-meter LTV height, and ~2.23 times based on 2.4-meter LTV height.

So we have come to estimate the size of Amphicoelias fragillimus:

First, the Diplodocus-based estimates:

Based on the ~28.5-meter length for A. altus, which was based on femur length and scaled from Diplodocus, we get:71.592 meters based on a LTV height of 2.7 meters for A. fragillimus,68.97 meters based on a LTV height of 2.6 meters, and,63.555 meters based on a LTV height of 2.4 meters.

Based on the ~25.4-meter length for A. altus, which was based on last trunk vertebra height and scaled from Diplodocus, we get:63.8048 meters based on a LTV height of 2.7 meters for A. fragillimus,61.468 meters based on a LTV height of 2.6 meters, and,56.642 meters based on a LTV height of 2.4 meters.

Now, for the Barosaurus-based estimates:

Based on the 33.04-meter length for A. altus, which was based on femur length and scaled from Barosaurus, we get:82.99648 meters based on a LTV height of 2.7 meters for A. fragillimus,79.9568 meters based on a LTV height of 2.6 meters, and,73.6792 meters based on a LTV height of 2.4 meters.

Based on the ~27.36-meter length for A. altus, which was based on last trunk vertebra height and scaled from Barosaurus, we get:68.72832 meters based on a LTV height of 2.7 meters for A. fragillimus,66.2112 meters based on a LTV height of 2.6 meters, and, 61.0128 meters based on a LTV height of 2.4 meters.

Now, the real issue is which vertebra height is most likely, for that, we must see the quote by Zach:

Thanks, and as Amphicoelias a. goes, its femur was measured at 1.77 meters, and supposedly had a total length of ~30 meters. According to Greg Paul. Running the numbers for Amphicoelias again, I seem to be getting numbers clustering in the 75-85 meter range. This is with an isometrically longer neck, but no additional intervertabral cartilage. Weights of 350 tons seem fully possible.

Based on CMNH10380, it would be about ~16.174 meters long with a mass of ~13.22 tonnes.

Based on CM572, it would be about ~16.88 meters long with a mass of ~13.93 tonnes.

Amphicoelias altus has a last trunk vertebra height of 1.075 m, and Amphicoelias fragillimus about 2.7 m, so based on the CMNH10380-based estimate, it would be about:~40.62 meters long, and ~209.46 tonnes in mass

Based on the CM572-based estimate, the size would be:~42.4 meters long, with a mass of ~220.71 tonnes

"Bullshits" is a word used only by you.Re-read my words, and please, stop such childish speculations in this blog.If you want to believe in super-giant sauropods based on nothing more than a problematic publication, it's your freedom. I don't care if you consider my conservative approach as "narrow-minded". You must provide more EVIDENCE of such animal, since this is how science works.

The possibility is still open though, as the discovered fossil record is puny compared to those that are undiscovered.

Not really, it's because if it had Brachytrachelopan's wimpy neck, it's feeding area would not be enough to sustain a massive body...

If Amphicoelias fragillimus was a gigantic ~30-meter Brachytrachelopan, then it would have a mass of approximately 185.19-370.37 tonnes*...a wimpy Brachytrachelopan-type neck isn't going to sustain it...

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